The Founders felt that it would be easier and more efficient to just create a new constitution and government rather than revising the Articles of Confederation.
The Articles of Confederation was the United States' first constitution. It was known for being very weak and giving little to no power to the federal government. With the Articles, the government could not tax the states, create and enforce laws properly, regulate trade, and other important matters.
Over time, people started to believe that the Articles of Confederation was harming the country and they needed something more powerful. The people who thought this were called Federalists. Anti-Federalists, on the other hand, preferred to have a weak government and often associated it with British tyranny.
The Constitutional Convention was called in 1787 and was originally meant to just simply revise the Articles of Confederation, but they ended up getting scrapped altogether for the United States Constitution.